GPR84 was recently isolated and characterized from human B cells (Wittenberger et al., 2001, J Mol Biol, 307, 799-813) as the result of an expressed sequence tag data mining strategy, and also using a degenerate primer reverse transcriptase-polymerase chain reaction (RT-PCR) approach aimed to identify novel chemokine receptors expressed in neutrophils (Yousefi S et al. 2001 J Leukoc Biol; 69, 1045-52).
GPR84 (also known as EX33) remained an orphan GPCR until the identification of medium-chain FFAs with carbon chain lengths of 9-14 as ligands for this receptor (Wang et al., (2006) J. Biol. Chem. 281:3457-64). GPR84 was described to be activated by capric acid (C10:0), undecanoic acid (C11:0) and lauric acid (C12:0) with potencies of 5 μM, 9 μM and 11 μM, respectively. Two small molecules were also described to have some GPR84 agonist activity: 3,3′ di-indolylmethane (DIM) (Wang et al. (2006) J. Biol. Chem. 281:3457-64) and embelin (WO 2007/027661A2).
GPR84 expression has been shown to be expressed in immune cells at least but not limited to polymorphonuclear leukocytes (PMN), neutrophils, monocytes, T cells, B cells. (Wang et al., 2006, The Journal of Biological Chemistry, 281, 45, 3457-3464, Yousefi et al., 2001, Journal of Leukocyte Biology, 69, 1045-1052, Venkataraman and Kuo, 2005, Immunology Letters, 101, 144-153, WO2007/027661 A2). Higher levels of GPR84 were measured in neutrophils and eosinophils than in T-cells and B-cells. GPR84 expression was demonstrated in tissues that may play a role in the propagation of the inflammatory response such as lung, spleen, bone marrow.
For example, in a recent review, Du Bois reported the current status of therapies for lung interstitial diseases, such as idiopathic pulmonary fibrosis (IPF). There are almost 300 distinct injurious or inflammatory causes of interstitial lung disease that can result in diffuse lung scarring, and the initial stages of the IPF pathology are very likely to involve inflammation (Du Bois, 2010, Nat Rev, Drug Discovery, 9, 129), and combination therapies involving anti-inflammatory treatment could be advantageously used.
The expression of GPR84 was highly up-regulated in monocytes/macrophages upon LPS stimulation (Wang et al., 2006, The Journal of Biological Chemistry, 281, 45, 3457-3464).
GPR84 knock-out (KO) mice are viable and indistinguishable from wild-type littermate controls (Venkataraman and Kuo, 2005, Immunology Letters, 101, 144-153). The proliferation of T and B cells in response to various mitogens is reported to be normal in GPR84-deficient mice (Venkataraman and Kuo, 2005, Immunology Letters, 101, 144-153). T helper 2 (Th2) differentiated T cells from GPR84 KO secreted higher levels of IL4, IL5, IL13, the 3 major Th2 cytokines, compared to wild-type littermate controls. In contrast, the production of the Th1 cytokine, INFγ, was similar in Th1 differentiated T cells from GPR84 KO and wild-type littermate (Venkataraman and Kuo, 2005, Immunology Letters, 101, 144-153).
In addition, capric acid, undecanoic acid and lauric acid dose dependently increased the secretion of interleukin-12 p40 subunit (IL-12 p40) from RAW264.7 murine macrophage-like cells stimulated with LPS. The pro-inflammatory cytokine IL-12 plays a pivotal role in promoting cell-mediated immunity to eradicate pathogens by inducing and maintaining T helper 1 (Th1) responses and inhibiting T helper 2 (Th2) responses. Medium-chain FFAs, through their direct actions on GPR84, may affect Th1/Th2 balance.
Berry et al. identified a whole-blood 393-gene transcriptional signature for active tuberculosis (TB) (Berry et al., 2010, Nature, 466, 973-979). GPR84 was part of this whole-blood 393-gene transcriptional signature for active TB indicating a potential role for GPR84 in infectious diseases.
GPR84 expression was also described in microglia, the primary immune effector cells of the central nervous system (CNS) from myeloid-monocytic origin (Bouchard et al., 2007, Glia, 55:790-800). As observed in peripheral immune cells, GPR84 expression in microglia was highly inducible under inflammatory conditions such as TNFa and IL1 treatment but also notably endotoxemia and experimental autoimmune encephalomyelitis (EAE), suggesting a role in neuro-inflammatory processes. Those results suggest that GPR84 would be up-regulated in CNS not only during endotoxemia and multiple sclerosis, but also in all neurological conditions in which TNFα or IL1b pro-inflammatory cytokines are produced, including brain injury, infection, Alzheimer's disease (AD), Parkinson's disease (PD).
GPR84 expression was also observed in adipocytes and shown to be enhanced by inflammatory stimuli (Nagasaki et al., 2012). The results suggest that GPR84 emerges in adipocytes in response to TNFα from infiltrating macrophages and exacerbates the vicious cycle between adiposity and diabesity, and therefore the inhibition of GPR84 activity might be beneficial for the treatment of endocrine and/or metabolic diseases.
Therefore, the present invention provides novel compounds, processes for their preparation and their use in the preparation of a medicament for the treatment of inflammatory conditions (for example inflammatory bowel diseases (IBD), rheumatoid arthritis, vasculitis, lung diseases (e.g. chronic obstructive pulmonary disease (COPD) and lung interstitial diseases (e.g. idiopathic pulmonary fibrosis (IPF))), neuroinflammatory conditions, infectious diseases, autoimmune diseases, endocrine and/or metabolic diseases, and/or diseases involving impairment of immune cell functions.